ipc/sem.c: handle spurious wakeups
Manfred Spraul [Wed, 2 Nov 2011 20:38:52 +0000 (13:38 -0700)]
semtimedop() does not handle spurious wakeups, it returns -EINTR to user
space.  Most other schedule() users would just loop and not return to user
space.  The patch adds such a loop to semtimedop()

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Reported-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ipc/sem.c

index fb13be1..227948f 100644 (file)
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1426,6 +1426,8 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
 
        queue.status = -EINTR;
        queue.sleeper = current;
+
+sleep_again:
        current->state = TASK_INTERRUPTIBLE;
        sem_unlock(sma);
 
@@ -1478,6 +1480,13 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
         */
        if (timeout && jiffies_left == 0)
                error = -EAGAIN;
+
+       /*
+        * If the wakeup was spurious, just retry
+        */
+       if (error == -EINTR && !signal_pending(current))
+               goto sleep_again;
+
        unlink_queue(sma, &queue);
 
 out_unlock_free: